DBC电子封装基板研究进展

综述了DBC电子封装基板的研究进展,介绍了DBC电子封装基板材料的选择、敷电子封装中的使用特点,并展望了DBC电子封装基板的应用前景.     

低温共烧基板材料研究进展

LTCC是现代微电子封装中的重要组成部分,因性能优良而广泛应用于高速、高频系统.LTCC基板材料的性能决定封装的质量,材料的研究在LTCC的进展中发挥了重要作用.LTCC基板材料可分为两大类:玻璃/陶瓷和微晶玻璃.概述了各类基板材料的组成、性能和应用方面的情况,并介绍了各类材料研究的进展,指出了基板材料未来的发展方向.     

功率型LED散热基板的研究进展

在与传统LED散热基板散热性能比较的基础上,分析了国内外功率型LED散热基板的研究现状,介绍了金属芯印刷电路板、陶瓷基板、金属绝缘基板和金属基复合基板的结构特点、导热性能及封装应用,指出了功率型LED基板材料的发展趋势及需要解决的问题.     

低温共烧陶(LTCC)技术在材料学上的进展研究

文章先分析了低温共烧陶技术,随后介绍了相关生产工艺中的基板、封装材料和布线材料,最后介绍了低温共烧陶技术的发展趋势,希望能给相关人士提供有效参考.     

大功率LED封装基板研究进展

随着大功率LED向高电流密度、高光通量发展,热流密度猛增使得LED散热问题日益严重。封装基板对LED的散热至关重要。在简介LED的封装结构及散热方式的基础上,分析总结了常见封装基板材料的性能参数,并对目前市场常见封装基板MCPCB、DBC、DAB、DPC、LTCC、HTCC、Al/SiC以及最近出现的新型材料基板的特征、制造工艺、应用等进行了综述。     

封装材料对PVDF薄膜传感器激波响应的影响

PVDF(聚偏氟乙烯)及其共聚物压电薄膜具有响应快、灵敏度高、测压范围宽等特点,为冲击波压力测试传感器提供了新的敏感材料.本文详细的介绍了PVDF薄膜传感器的制作过程,并对封装用的粘结剂以及外保护层进行了激波管的对比试验,考察封装材料对PVDF薄膜传感器动态性能的影响.通过对试验数据的判读,确定了较为合适的封装粘结剂及保护层材料.     

性能优异的多功能宽禁带半导体AlN薄膜

作为具有优异介电性、压电性的宽禁带半导体材料,ＡｌＮ是重要的电子封装材料、绝缘介质材料、声表面波材料和蓝光紫外发光材料。本文介绍了ＡｌＮ材料结构特性、薄膜制备及应用的最新进展     

宽带驱动放大器MMIC的SMD封装

研究了一种采用Rogers 4003型有机基板材料和PCB工艺制造的MMIC一级封装结构,该封装结构与SMT工艺兼容,具有良好的散热性能和较低的成本,可用于X＆Ku波段驱动放大器芯片.采用三维电磁场仿真软件对封装结构进行了优化设计,制备了封装结构样品,并采用HP 8722D型高频网络分析仪实测了封装后的X＆Ku波段驱动放大器芯片性能.测试结果表明,在6～18GHz频段内,封装后芯片的增益维持在20dB以上,反射小于-10dB,性能与裸芯片十分接近.关键词:MMIC,封装,有机基板材料,SMT,三维电磁场仿真     

硅氧碳纳米镶嵌复合薄膜的氧空位形成与散热基板封装

自支撑硅氧碳纳米镶嵌复合薄膜具有细小等轴β-SiC纳米晶弥散分布在非晶态相SiO_xC_y和游离碳基体的复合结构。利用电子顺磁共振谱(EPR)仪对900~1 200℃终烧薄膜复合结构中的氧空位形成进行分析;采用丝网印刷法在薄膜表面获得两条平行高温银浆电路层,并以其为散热基板进行LED器件板上芯片封装(COB)。通过扫描电镜(SEM)与光学显微镜对薄膜微观形貌及封装结构进行观察,并通过LED热光参数测试仪对其结温进行探究。结果表明,终烧温度升高,薄膜氧空位浓度增大,g因子接近自由电子值2.0023。高温银浆导电层均匀致密保证良好电导效果。1 200℃终烧薄膜作为散热基板具有较好热传导与绝缘特性,其封装LED结温约为33.7℃,低于120℃限制,有望规模应用于大功率LED器件领域。     

改善PCB高密度基板封装质量的研究

高密度基板上的微孔质量对封装微电子器件十分重要,由于孔密度大,孔径又小,目前普遍采用激光打孔。针对基板的组成材料以及激光加工中主要参数对微孔加工的影响进行分析研究。通过不同材料粘结力和改变激光的功率、脉宽等措施,改善基板电子元器件封装的质量。     

PP/LCP复合材料的物性及力学特性

通过对容易再生的PP/LCP复合材料的微观结构、动态粘弹性特性、热膨胀特性以及力学特性进行讨论,明确了PP/LCP虽为不相溶的两相复合材料,但由于PP和LCP相的热膨胀系数不同,使两相具有比较好的界面结合强度。当LCP加入量低于40 ％时,形成以PP为基LCP为纤维状的强化相并沿流动方向分布。LCP的含量高于60 ％后,PP相的存在对复合材料的延性及强度均带来不利影响。      

LCP微球对LCP/尼龙6共混体系力学性能的影响

制备了分散相呈球状微粒形貌的液晶聚合物/尼龙6 (LCP/PA6)共混体系,选用离聚物磺化聚苯乙烯锌盐(Zn-SPS)和反应性嵌段共聚物苯乙烯-马来酸酐共聚物(SMA)作为体系的增容剂,探讨了在相间相互作用得以改善时,利用LCP微球改善 LCP/尼龙6 共混体系韧性的可能性。试样受拉后的形貌观察表明,在增容体系中,LCP微球很好地镶嵌在尼龙6基体中,粒子脱落的空洞发生了较大的形变。力学性能测试结果表明,LCP的加入使材料的拉伸强度低于纯尼龙6,加入增容剂后共混材料拉伸强度有所提高,其中LCP/PA6 (质量比10/90)共混体系增容后的拉伸强度与纯尼龙6 相当。所研究的增容体系的拉伸断裂吸收能均比未增容体系有所增加。其中,当 LCP的质量分数为4%时,Zn-SPS增容体系的拉伸断裂吸收能比未增容体系和纯尼龙6分别增加了12%和62%;当LCP的质量分数为10 %时,SMA增容体系的拉伸断裂吸收能比未增容体系和纯尼龙6分别增加了46%和55%。表明在适当条件下,利用LCP微球可以在保持共混体系的拉伸强度的同时提高材料的韧性。     

Mechanical properties of injection moulded blends of polypropylene with thermotropic liquid crystalline polymer

Blends of a thermotropic liquid crystalline polymer (LCP) with polypropylene (PP) were injection moulded. The LCP exhibited a higher viscosity than that of PP. Static and dynamic mechanical measurements, Izod impact tests, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were performed on these blends. The static tensile tests show that the tensile modulus and strength of PP are improved with the addition of LCP. The improvement in mechanical properties is associated with the formation of LCP fibrils as evidenced by SEM observations. Dynamic studies on these blends show an increase in the storage modulus but a decrease in loss factor with the addition of LCP. Furthermore, TGA measurements show that the thermal stability of PP is improved substantially with the addition of LCP.     

Structure formation and miscibility of sheets from PBT and LCP blends

Sheets from blends containing poly(butylene terephthalate) (PBT) and liquid crystalline polymer (LCP) were prepared using a twin-screw extruder. The LCP used is a copolymer composed of 20 mol % ethylene terephalate (PET) and 80 mol % p-hydroxybenzoic acid (PHB). Thermal behavior, viscoelastic properties, and structure of the sheets of various compositions were investigated by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), microwave orientation analysis (MOA), and wide angle x-ray diffraction (WAXD). X-ray diffractograms of extruded sheets from PBT, LCP, and their blends show a high degree of orientation along extrusion direction. The orientation is mainly due to the high crystallization rate of PBT, although crystallization and orientation of PBT in the PBT and LCP blends could also be induced by adding LCP. In the PBT and LCP blends, the thermal properties of the constituents are slightly changed indicating that PBT and LCP are partially miscible. DSC measurements show that as the amount of LCP added to the blend increased, the melting point T _m of PBT in the blends decreased. The single glass transition temperature T _g for the PBT and LCP was observed by DMA. Furthermore, no evidence of transesterification in PBT and LCP blends was observed by WAXD.     

Neural signal recording using microelectrode arrays fabricated on liquid crystal polymer material

Microelectrode arrays have been developed for simultaneous multi-channel recordings from nervous systems, typically using silicon substrates. However, it has been known that it is difficult to meet the biocompatibility and durability requirements using silicon and other dielectric materials (SiO₂, Si₃N₄), due to environmental moisture and ions. Additional disadvantage of silicon being the rigid material makes it hard to apply these materials in chronic recording situations.Liquid Crystal Polymer (LCP) was recently introduced as a candidate material for electronic packaging purposes. The material acts as efficient barrier against ions and moisture, a desirable feature for a substrate material of microelectrode arrays. In this paper, we report on the neural recording performed using the LCP-based microelectrode arrays.The cell adhesion on the new material was compared very favorably with that using silicon, SiO₂, or polyimide material. The microelectrode arrays were patterned with Ti (500 Å)/Au (3500 Å) on the LCP film and were employed in both stimulation and recording from rat sciatic nerve. The electrical characteristic of the recorded signal was as good as those using other substrate materials, proving this material as an excellent candidate for next generation microelectrode arrays.     

Impact of plasma etching on fabrication technology of liquid crystal polymer printed circuit board

Liquid crystal polymer (LCP) has attracted great attention as a potential candidate for high performance micro-wave substrate material in high frequency printed circuit boards (PCB). This is attributed to its low loss behaviour, excellent thermal stability, and outstanding chemical resistance. The use of LCP in PCB, however, is hindered by its extreme chemical inertness, causing fabrication challenges in desmearing and metallization processes. To overcome the challenges, plasma etching is suggested for its capability of smear removal, adhesion improvement and surface activation of PCB material. However, previous experimental and theoretical studies of the effects of plasma etching on LCP PCB at different treatment conditions are lacking. This paper thus evaluates recent developments on plasma etching technologies, involving the plasma etching investigation under different process conditions for manufacturing LCP PCB. Distinct process approaches are developed and proposed based on the illustrations of the experimental outcomes. Finally, examples are shown to demonstrate the effectiveness of the proposed plasma etching approach for controlling the fabrication of LCP PCB.     

PP/LCP composites: effects of shear flow,extensional flow and nanofillers

PP/LCP composites moulded under shear flow and extensional flows were prepared in this work. It was observed that the predominating shear flow during injection moulding was unable to induce in-situ reinforcements in the Rodrun LC5000/PP blend. With the introduction of an additional drawing process, fibrous LCP was developed. The fibrillation of the LCP phase was found to increase with the draw speed and the formation of LCP fibrils was manifested as higher strength and stiffness. However, due to the poor adhesion between the pre-generated LCP fibrils and PP matrix, the strength of the extensional PP/LCP composites was lower than that of direct injection moulded LCP/PP blend. In another approach, silica fillers were introduced to the LCP/PP blend and the LCP fibrillation was found to improve. The nanosilica was believed to behave as a viscosity thickening agent and was able to promote the LCP droplet-fibril transition effectively. The nanofiller/LCP/thermoplastic system possessed dual reinforcements which imparted good properties to the composite.     

Linearly coded profilometry with a coding light that has isosceles triangle teeth: even-number-sample decoding method

A new triangulation-based optical profilometry-linearly coded profilometry (LCP)-is presented. In this method, a linear coding technique is introduced. It uses a periodic sawtoothlike structure light to code the surface being measured and the phase-shifting technique to decode the profile. A coding light that has isosceles triangle teeth is proposed. To realize the decoding, at least three samples are needed. When more than three samples are used, higher accuracy can be obtained. A decoding method of LCP with an even number of samples is provided. This method has been realized in my laboratory and the experimental results verify the reliability of LCP. Because the coding method used in LCP is simpler than that used in phase-measuring profilometry, LCP has a faster measuring speed.     

Optimal EWMA of linear combination of Poisson variables for multivariate statistical process control

In this paper, we propose a new process control chart for monitoring correlated Poisson variables, the EWMA LCP chart. This chart is the exponentially weighted moving average (EWMA) version of the recently proposed LCP chart. The latter is a Shewhart-type control chart whose control statistic is a linear combination of the values of the different Poisson variables (elements of the Poisson vector) at each sampling time. As a Shewhart chart, it is effective at signalling large process shifts but is slow to signal smaller shifts. EWMA charts are known to be more sensitive to small and moderate shifts than their Shewhart-type counterparts, so the motivation of the present development is to enhance the performance of the LCP chart by the incorporation of the EWMA procedure to it. To ease the design of the EWMA LCP chart for the end user, we developed a user-friendly programme that runs on Windows© and finds the optimal design of the chart, that is, the coefficients of the linear combination as well as the EWMA smoothing constant and chart control limits that together minimise the out-of-control ARL under a constraint on the in-control ARL. The optimization is carried out by genetic algorithms where the ARLs are calculated through a Markov chain model. We used this programme to evaluate the performance of the new chart. As expected, the incorporation of the EWMA scheme greatly improves the performance of the LCP chart.     

PVDF、LCP及其共混物的流变行为

研究了ＰＶＤＦ、ＬＣＰ的表观粘度随温度,剪切速率的变化规律,并对液晶含量对共混物熔体度的影响进行了讨论。